export default (function (o, c) {
  var proto = c.prototype

  proto.weekYear = function () {
    var month = this.month()
    var weekOfYear = this.week()
    var year = this.year()

    if (weekOfYear === 1 && month === 11) {
      return year + 1
    }

    if (month === 0 && weekOfYear >= 52) {
      return year - 1
    }

    return year
  }
})
